Much development work has been done in connection with delivery fuel to internal combustion engines, in particular in recent years, the delivery of combustible fuel and gas, especially air, in metered quantities. Much of the work has centered around the delivery of a fuel mixture to two-cycle, spark ignition engines. U.S. Pat. No. 4,693,224 (Sep. 15, 1987) and U.S. Pat. No. 4,825,828 (May 2, 1989) illustrate and describe the problems of fuel injection and the advantages of direct in-cylinder injection which is effective in operation, economic to manufacture and achieves and maintains acceptable atomization of the fuel.
The present invention is specifically directed to spark ignited, internal combustion engines where a premetered quantity of fuel is entrained in a gas, conveniently air, and the fuel entrained in the gas is delivered directly into the combustion chamber of the engine through a nozzle which is intermittently opened. This is achieved by the use of a poppet valve which is controlled and moved axially to open and closed positions using an electromagnetic coil and an armature closely associated with the poppet valve. Each cylinder, in a multi-cylinder engine, is provided with a fuel and air nozzle injection assembly.
The present invention is directed to the construction of the solenoid which is used to actuate the poppet valve. The solenoid bobbin assembly is housed in a case and cover. It is known to mold plastic simultaneously externally and internally of the solenoid assembly and some of the problems in connection with this involve the pressure and heat needed. This may result in winding bobbin distortion which may cause seal failures. Another problem lies in the possibility of plastic resin flowing to areas where it cannot be tolerated or allowing fuel leakage past the seals to the outside of the injector.
Other manufacturers of fuel injectors have used injection molding into the solenoid assembly by leaving an end of the solenoid open so that when inserted into the mold, the mold can be used as a back-up for the bobbin to prevent distortion and to prevent mold material from flowing into areas where it cannot be tolerated.
The present invention is directed to a combination of an internal and external molding process which is accomplished without any internal mold support for the solenoid bobbin assembly. With the proposed process, damage to critical areas of the solenoid case and cover is avoided by eliminating the use of a support mandrel.
Other objects and features of the invention will be apparent in the following description and claims in which the principles of the invention are set forth together with details to enable persons skilled in the art to practice the invention, all in connection with the best mode presently contemplated for the invention.